Understanding the extent of morphological variation across diverse habitats and species can provide valuable insights into how organisms respond to environmental gradients. We quantified intraspecific morphological variation of unionid mussels and assessed how it varied in relation to genetic differentiation and environmental characteristics.
Mobile and Tennessee River Basins, Alabama and Tennessee, U.S.A.
Unionid mussels.
We used innovative three-dimensional (3D) scanning techniques and 3D geometric morphometric analyses, genetic data and environmental variables to quantify morphological variation in seven freshwater mussel species populations and its relationship to genetic differentiation and environmental characteristics.
Our findings indicate that shell morphological variation is correlated with environmental variables in four unionid species, and generally not related to genetic differentiation, improving our understanding of the mechanisms behind morphological variation. Three closely related species were more inflated in larger watersheds, while a more distantly related species, A. plicata, was more compressed in larger watersheds. River bankfull width was a significant factor in all models, highlighting the influence of high flow extremes on shell morphological variation.
Our findings suggest that environmental factors, particularly characteristics of river flow regimes, are the primary drivers of intraspecific shell morphological variation in unionid mussels, with genetic differentiation playing a less prominent role. Continuing to explore intraspecific trait variation along river gradients will improve our understanding of the ecological implications of shell morphological variation. Assessing the ability of organisms to morphologically adapt to environmental change can help us understand their resilience.
This work focused on the multi-scale distributional patterns of multi-dimensional diversity among different groups of amphibians in China and systematically investigated the underlying environmental driving mechanisms by evaluating the performance of multiple ecological hypotheses.
China.
Amphibians.
We examined the effects of different spatial scales on the distribution patterns of taxonomic, functional and phylogenetic diversity of amphibians. Additionally, we assessed the relative importance of eight hypotheses in explaining these multi-scale diversity patterns using hierarchical partitioning.
The spatial distributional patterns of amphibian taxonomic, functional and phylogenetic diversity exhibited scale dependency. Generally, the explanatory powers of hypotheses-related covariates increased with larger spatial grain sizes. Across eight spatial grains (ranging from 0.25 to 2 arc-degree), energy availability and spatial effect emerged as principal determinants for different amphibian groups in China. This was consistent for all species (469 species), as well as endemic, threatened and both endemic and threatened species.
Multi-group biodiversity patterns are characterised by multi-dimensional components and exhibit multi-scale dependency. Our study highlights the significant influences of spatial scale on biodiversity pattern and on the explanatory power of ecological hypotheses. These findings provide valuable insights for future conservation planning of amphibians in China.
A primary question for researchers in the field of conservation science concerns the fragmentation of biodiversity-supporting habitat. Key debates revolve around the relevance of habitat composition and configuration for conservation outcomes. Central to this debate is the measurement and delineation of the habitat patch, which informs fragmentation-related metrics and their evaluation. Despite the need to quantify and model habitat fragmentation, the habitat patch concept itself has been subject to criticism concerning its ability to adequately reflect the heterogeneity of resource distributions in complex landscapes. In this paper, we present the continuity-contiguity problem, which is one of the fundamental challenges related to the delineation of habitat in space, and discuss its implications for fragmentation-biodiversity research. We outline the potential contribution of recent developments in spatial-ecological methods and the leveraging of uncertainty in the modelling process to address four common issues related to the habitat patch concept: the gap-crossing problem, the need for multi-variate habitat delineation, the delineation of interior-edge transitions and the need to parameterise habitat as both a discrete and continuous spatial entity. We conclude with several recommendations for studies on fragmentation-biodiversity outcomes where the continuity-contiguity problem may influence the research process.
Despite the evidenced importance of insects in savannah ecosystems, the drivers of their diversity patterns remain poorly understood, particularly in the Afrotropical region. This study addresses part of this gap by investigating the effects of climate, habitat, disturbance and vegetation variables on species richness and community composition of phytophagous and predatory insects in South African savannahs.
Kruger National Park (KNP), South Africa.
Phytophagous insects (moths) and carnivorous insects (mantises).
Moths and mantises were light-trapped in 60 plots distributed across KNP during two seasons. Direct and indirect effects of environmental variables on insect species richness were analysed using structural equation models, and on community composition through distance-based redundancy analyses (db-RDA).
Based on an extensive dataset of 65,593 moth individuals representing 817 species and 3511 mantis individuals representing 38 species, we identified plant communities as the primary driver of species richness and community structure for both insect groups. The effects of vegetation on insect communities were indirectly shaped by climate, particularly mean temperature (negatively correlated with precipitation), through its effects on plant species richness. Additionally, a complex interplay among bedrock type, water availability and disturbance from large herbivores further shaped insect diversity.
Our findings highlight the critical role of plant species richness in determining insect diversity patterns in savannah ecosystems. We also confirmed the region's vulnerability to climate change, as decreasing precipitation and increasing temperatures alter vegetation composition and biomass, consequently affecting insect communities. Effective conservation strategies should focus on managing large herbivores to maintain diverse vegetation, which is crucial for supporting insect diversity. Priority should be given to balancing water availability and disturbance intensity, particularly in preserving the health of rivers and their surroundings, to mitigate the adverse effects of climate change on these ecosystems.
How is the local species richness of woody specialists in vegetation plots located within subtropical montane cloud forests (SMCFs) affected by the landscape structure of the surrounding SMCF habitat patch?
Subtropical montane cloud forests in Taiwan.
Woody species specialised in growing in foggy conditions.
We used plant occurrence data from major herbaria together with fog frequency data to identify fog specialists of SMCFs in Taiwan. Subsequently, we extracted 20 × 20 m forest vegetation plots from the National Vegetation Database of Taiwan and calculated the richness of woody specialists in each of them. Using a published predicted SMCFs distribution map, we estimated the landscape context of SMCFs around each vegetation plot within circular buffer zones of increasing radius. The variables of landscape structure include those related to the area of SMCFs habitat (area and connectivity), surrounding heterogeneity (topographical heterogeneity and vegetation diversity) and edge effect (the nearest distance from the plot to the edge and the edge length). The multiple linear regression model was used to investigate which of the three mechanisms of landscape context has the strongest effect on the local richness of fog specialists.
Only the area of SMCFs habitat patch shows a significant positive effect on the local species richness of woody specialists in the plot when considering all the landscape variables. Area per se might be a possible mechanism that supports this positive species-area relationship. Additionally, the area of SMCFs patch is highly correlated with connectivity, indicating that larger SMCF patches enhance connectivity beyond buffer zones, sustaining species through the rescue effect from the regional species pool.
Patch size and connectivity are crucial for the species richness of woody specialists in SMCFs in Taiwan. For conservation, we recommend protecting larger, less fragmented SMCF patches to maintain biodiversity.
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